1. Field of the Invention
This invention relates generally to a process and apparatus for preparing waste paper for reuse in a a paper machine, of the type including coarse pulping in a pulper, preliminary sorting, thickening to stock densities of more than 10%, treatment in a reaction tower in the presence of de-inking chemicals, followed by thinning of the suspension and flotation in flotation apparatus.
2. Description of the Prior Art
A process and apparatus of the type described above is disclosed, for instance, in German Laid-open patent specification DE-OS No. 2 311 674. In that process and apparatus, the de-inking chemicals are introduced to the pulp shortly before the reaction or bleaching tower, only chemicals used as sequestering agents being added in the pulper. With this process and apparatus, although a relatively high level of whiteness is obtained in the re-made paper, it is desirable to achieve still higher levels of paper whiteness.